Elastin derived from histologically defined regions of normal and pathological pulmonary and vascular tissues is under investigation. A new procedure for the examination of the complex crosslinks inelastin is also under development. Associated with elastin in vascular and pulmonary tissues, one can find in certain pathological states deposition of ectopic metastatic or dystrophic concretions contaning calcium as hydroxyapatite. In these concretions or "hardened" plaques, we have found a matrix protein(s) which contains gamma-carboxyglutamic acid, the recently discovered viamin K-dependent calcium binding amino acid. Studies are in progress to evaluate the origins and roles of these proteins in the calcification mechanism. Initial investigations involved human material obtained from the hardened atheromatous aortas. Current studies, in addition to human material, employ calcified vascular tissues from various animal models such as the white Carneau pigeon and various atherosclerotic primates. Proteins containing gamma-carboxyglutamate derived from these tissues are being isolated and purified.